Conveyor and plant for baling paper pulp

ABSTRACT

Conveyor systems are disclosed including a chain conveyor for carrying a predetermined load, a frame for the chain conveyor, a track, wheels for supporting the frame for movement along the track from a predetermined reference position, the chain conveyor being movably supported on the frame for movement from the predetermined reference position, and sensors for detecting the position of the conveyor along the track with respect to the first predetermined reference position without direct contact, or for detecting the position of the chain conveyor with respect to the second predetermined reference position without direct contact, the sensors delivering a train of pulses corresponding to a predetermined distance of movement of the conveyor along the track or of movement of the chain conveyor with respect to the frame, whereby the position of the conveyor along the track or of the chain carrier can be determined.

FIELD OF THE INVENTION

The present invention relates to a conveyor with a frame supporting acarrier device for carrying a load. More particularly, the presentinvention relates to such a conveyor supported by motor-driven wheels toeffect traveling movement along a predetermined track and/or the carrierdevice being movably supported in relation to the frame of the conveyor.Still more particularly, the present invention also relates to a plantfor baling paper pulp.

BACKGROUND OF THE INVENTION

It is well know in the art that driving motors for the movement ofconveyors, as well as driving motors for carrier devices on the conveyorframe, can be stopped in different stop positions by the action ofmechanically mounted limit positions. The limit positions communicatewith contactors, for example, which activate the driving motors. Whenthe contactors are in “on” position the driving motors run at full speedand are stopped when the contactors, under the influence of the limitpositions, are caused to assume the “off” position. However, movement ofthe conveyor and/or of the carrier device is stopped with a certain timedelay, which means that precision in stopping in the path of travel ofthe conveyor or of the carrier device on the conveyor is generally poor.Stopping thus sometimes occurs “too early” in the actual movement, andsometimes “too late.” The location of the limit position in the path oftravel of the conveyor and/or the limit positions of the carrier devicemust then be mechanically adjusted so that stopping occurs at theintended location. Adjusting the limit positions in this manner isimpractical and time-consuming.

It is often desirable for the conveyor to be stopped at several pointsalong its path of travel and/or for the carrier device to be stopped atseveral points in relation to the conveyor frame. It is known in the artthat this can be realized by permitting the traveling movement of theconveyor, or carrier device movement, to continue for a specified timeand then be stopped, which is hardly an exact method. Alternatively,several stop locations can be determined by means of limit positionsarranged at these stop locations. The problems which are encounteredwith such an arrangement are particularly difficult in the case of theactual traveling movement of the conveyor. Limit position indicatorsmust therefore be used to provide a number of “preparatory” limitpositions before a stop position, in order to indicate that the speedmust be reduced, and the driving motor must be stopped at some wayconsiderably before the actual stop position, since the conveyor willcontinue its movement due to inertia. The load on the conveyor is alsoof significance in this regard. The conveyor must often thus be pulledto the actual stop position with the aid of hydraulic devices after thedriving motor has been stopped. Another drawback is that the situationis different when the conveyor is traveling in the opposite direction.The result is that a very large number of limit positions is required.For five stop positions, for instance, thirteen limit positions arerequired, including preparatory limit positions.

Present technology renders it difficult to set correct stop positionsfor the conveyor movements since these are dependent on the performanceof the driving motor, the cycle time of the control program, thefriction on the rails and the total weight of the conveyor, which isalso dependent on the size of the load.

Considerable precision in the movement of the conveyor is thus requiredfor many applications, e.g. baling paper pulp. Several bales must oftenbe placed on the carrier device one at a time. It is then of greatimportance that the distribution of or the spacing between the bales isalways substantially the same. The bales must also be well centered onthe conveyor during transfer from one conveyor to the next. The greaterthe precision in this respect, which is thus determined by the carrierdevice being stopped at the correct positions, the simpler will besubsequent handling with machines, trucks and the like.

One object of the present invention is to thus eliminate theabove-discussed drawbacks in known conveyors.

SUMMARY OF THE INVENTION

In accordance with the present invention, this and other objects havenow been realized by the invention of a conveyor system comprising aconveyor including carrier means for carrying a predetermined load, aframe for the carrier means, a track, wheel members supporting the framefor movement along the track from a predetermined reference position,and sensor means for detecting a position of the conveyor along thetrack with respect to the predetermined reference position withoutdirect contact therewith, the sensor means delivering a train of pulsescorresponding to a predetermined distance of movement of the conveyoralong the track, whereby the position of the conveyor along the trackcan be determined. In a preferred embodiment, the conveyor systemincludes a driving motor for moving the conveyor along the track, andthe sensor means are positioned to detect the rotation of the wheelmembers along the track or the rotation of the driving motor.

In accordance with one embodiment of the conveyor system of the presentinvention, the conveyor system includes a plurality of detection pointsdisposed along the track for detection by the sensor means. Preferably,the plurality of detection points comprise a plurality of openingsevenly spaced along the track.

In accordance with another embodiment of the conveyor system of thepresent invention, the conveyor system includes speed control means forcontrolling the speed of movement of the conveyor along the track basedupon the train of pulses determined by the sensor means.

In accordance with another embodiment of the conveyor system of thepresent invention, the carrier means comprises a chain conveyor.

In accordance with another embodiment of the conveyor system of thepresent invention, the driving motor comprises a reversible drivingmotor, whereby the direction of movement of the conveyor along the trackcan be reversed.

In accordance with another embodiment of the conveyor system of thepresent invention, the sensor means comprises conductive pulsetransducer means for detecting conductive changes and determining thecorresponding train of pulses based thereon.

In accordance with another embodiment of the conveyor system of thepresent invention, the conveyor system is used in the baling of paperpulp.

In accordance with the present invention, a conveyor system has beendiscovered which comprises a conveyor including carrier means forcarrying a predetermined load, a frame for the carrier means, thecarrier means being movably supported on the frame for movement from apredetermined reference position, and sensor means for detecting theposition of the conveyor means with respect to the predeterminedreference position without direct contact therewith, the sensor meansdelivering a train of pulses corresponding to a predetermined distanceof movement of the carrier means with respect to the frame, whereby theposition of the carrier means can be determined. In a preferredembodiment, the conveyor system includes a plurality of motor drivengear wheels for movably supporting the carrier means with respect to theframe. Preferably, the conveyor system includes a driving motor fordriving the motor driven gear wheels, and the sensor means arepositioned to detect the rotation of the motor driven gear wheels or therotation of the motor.

In accordance with one embodiment of the conveyor system of the presentinvention, the conveyor system includes a plurality of detection pointsdisposed along the carrier means for detection by the sensor means.Preferably, the plurality of detection points comprises a plurality ofopenings evenly spaced along the carrier means.

In accordance with another embodiment of the conveyor system of thepresent invention, the conveyor system includes speed control means forcontrolling the speed of movement of the carrier means along the framebased upon the train of pulses determined by the sensor means.

In accordance with another embodiment of the conveyor system of thepresent invention, the driving motor comprises a reversible drivingmotor whereby the direction of movement of the carrier means withrespect to the frame can be reversed.

In accordance with another embodiment of the conveyor system of thepresent invention, the conveyor system includes a plurality of endposition indicators for stopping movement of the carrier means along theframe at predetermined end positions.

In accordance with another embodiment of the conveyor system of thepresent invention, the sensor means comprise inductive pulse transducermeans for detecting inductive changes and determining the correspondingtrain of pulses based thereon.

In accordance with another embodiment of the conveyor system of thepresent invention, the conveyor system is used in the baling of paperpulp.

In accordance with the conveyor system of the present invention,traveling movement is determined from a zero or reference position andsensors are arranged for contactless detection of the position of theconveyor on the track by counting pulses, one pulse corresponding to acertain distance. The direction of movement of the driving motor is alsoknown.

In accordance with a preferred embodiment of the present invention, theposition of the conveyor can be detected by measuring the rotation ofthe driving motor or the wheels. The position can also be measured withthe aid of points along the track of the conveyor, in the form ofopenings spaced evenly along a strip, which the sensor thus detects.Alternatively, the strip may be provided with light and dark lines orbands which are detected one after another by a sensor on the conveyoror carrier device in order to sense movement in this manner. Theabove-mentioned technology, with fixed points, lines or the like alongthe path of movement provides a reliable way of determining the positionof the conveyor since the actual position is detected, as opposed to thecase where the position is determined from the rotation of the drivingmotor or wheels. If the wheels were to slip in the latter case, forinstance, determination of the position would be incorrect.

In accordance with the present invention, the position of the carrierdevice can be detected by measuring the rotation of the driving motor orof the gear wheels. Only one limit position is thus required at each endof the carrier device in order to obtain starting points to determinethe relative position of the carrier device after the load hasinfluenced the limit position.

The conveyor system in accordance with the present invention offers notonly functional improvements but also advantages from the points of viewof both manufacturing and installation. With the conveyor system inaccordance with the present invention the stop positions are thusdetermined by means of software instead of physically, as withpreviously known technology. This means that all conveyors can be madethe same, thereby facilitating standardization, thus improvingmanufacture. Installation and start-up of the conveyor movements can nowbe performed more quickly, since no physical stop positions need bemoved and adjusted, and the load on the conveyor carrier device can betaken into consideration when controlling the movements of the conveyor.

The pulse transducer technology in accordance with the present inventionis also well suited for use in connection with so-called frequencyoperation of the driving motors. During such frequency operation thespeed of the driving motor is controlled by means of pulses which havevarying on and off times. The motor speed can thus be optionallycontrolled from standstill up to full speed, and smooth starting andstopping movements can be achieved so the load is not displaced. Higherspeeds can be used for movements of the conveyor, and the speed can begradually reduced so that the desired stop position is reached exactly.The capacity of the plant is also increased in relation to knowntechnology if conveyors comprising pulse transducer technology are usedin a baling line, for instance.

According to an advantageous embodiment of the conveyor system inaccordance with the present invention, the sensors comprise inductivepulse transducers which are arranged to detect inductive changes whenthe wheels or driving motors are rotating. These pulse transducers areextremely reliable and are particularly well suited for industrialapplications, and since detection occurs contactless, there is no wearor abrasion. The pulse transducers are accurate and are protected fromvibrations, dampness and dirt, and can therefore be advantageously usedin difficult environments.

The invention present also relates to a plant for baling paper pulp.

BRIEF DESCRIPTION OF THE DRAWINGS

To further explain the present invention, reference is made to thefollowing detailed description, which, in turn, refers to theaccompanying drawings, in which

FIG. 1 is a side, perspective view of a conveyor system in accordancewith the present invention;

FIG. 2 is a side, perspective view of another conveyor system inaccordance with the present invention;

FIG. 3 is a side, perspective view of yet another conveyor system inaccordance with the present invention; and

FIG. 4 is a front, sectional view demonstrating use of the sensors inconnection with the conveyor system in accordance with the presentinvention.

DETAILED DESCRIPTION

Referring to the Figures, in which like reference numerals refer to likeelements thereof, the embodiments of the conveyor system in accordancewith the present invention shown in FIGS. 1-3 are primarily intended foruse in a plant for baling paper pulp.

FIG. 1 shows a stationary chain conveyor with a carrier device in theform of two conveyor chains, 32 and 34. The chains, 32 and 34, aresupported by gear wheels attached to the conveyor frame 8 and driven bya driving motor 6. Spring limit position indicators, 10 and 12, arearranged at the ends of the conveyor. When a load is passed onto one endof the conveyor it affects the limit position at this end and this isthen used as zero or reference position.

Sensors, preferably inductive pulse transducers of a type shown in FIG.4, are arranged to detect the rotation of the gear wheels forestablishing the rotation of the conveyor chains, 32 and 34, in relationto the zero or reference position. The zero or reference position on theconveyor in question, where the load at present is on the chain, is usedas the point of departure and emitted from this zero or referenceposition the number of pulses is then counted in order to obtain theactual position.

The limit position where the load leaves the conveyor is used as asafety device so that the load does not fall off the conveyor.

The driving motor 6 for the conveyor chains, 32 and 34, is connected, bymeans of gear wheels and separate drive chains (not shown in thefigure), to a shaft common to both chains, 32 and 34, so that they arealways driven at the same speed. A separate tensioning device ispreferably arranged for each chain to ensure correct individual tensionin each chain.

FIG. 2 shows a traveling conveyor, carried on wheels enabling it toperform traveling movement along a predetermined track. The track maysuitably be formed by rails, 14 and 16. A drive motor 18 is arranged todrive at least one of the wheels supporting this traveling conveyor inorder to propel it along its track, 14 and 16.

Sensors of the type shown in FIG. 4 are preferably arranged inside thegearbox of the driving motor 18, so that the position of the conveyor onthe track, starting from a zero or reference position, can easily bedetermined by counting the pulses from the sensor. The sensors may,however, be arranged in any movable part of the motor.

The direction of travel of the conveyor and/or the direction of movementof the carrier device in relation to the conveyor frame can bedetermined through knowledge of the direction of rotation of the drivingmotor, or alternatively, by two phase-shifted pulse trains.

The traveling conveyor shown in FIG. 2 is in all other respects also achain conveyor of a type similar to that shown in FIG. 1.

FIG. 3 shows another example of a conveyor in accordance with thepresent invention. This conveyor is of the turning or swiveling type,i.e. similar to the traveling conveyor in FIG. 2 except that the trackis circular and the movement therefore comprises a turning or swivelingmovement. In the same way as in FIG. 2 the conveyor is supported bywheels on a rail 26 which, in this case, is curved in a circle. Thedriving motors 6 and 28 are normally asynchronous electric motors,connected to the wheels by means of toothed transmission gears, aninductive pulse indicator being arranged on the driving motor shaft.

All driving motors in the conveyors described above are reversible forswitching the direction of movement for both the traveling movement andthe movement of the chains.

The examples of conveyors shown in FIGS. 1-3 can be modified and variedin many ways. Thus, the width of the conveyor and the number of chainsmay be increased, for instance, and the length of the conveyor may bevaried. This offers great flexibility in constructing various conveyorsystems.

In order to detect the rotation of the driving motors, 6 and 18, sensorsare used, such as those of the type described in the brochure “ifm,inductive proximity switches,” ifm Catalogue 1997/1998, which emit pulsetrains depending on the rotation of the motor. FIG. 4 shows theprincipal structure of such a sensor in the form of an inductive pulseindicator comprising a ferrite core 1 with an inductive coil 2. The core1 and the coil 2 are enclosed in a casing 3, and the electromagneticfield around the sensor is illustrated at 4.

The coil 2 and ferrite core 1 form the inductive part of a tuned LCcircuit that drives an oscillator. The coil 2 and core 1 generate alow-energy electromagnetic field 4 on the sensor side of the pulsetransducer. When an electric conductor, such as a metal object, entersthis field, eddy currents are generated in the conductor. These eddycurrents draw energy from the field 4, and when the eddy currents becomeso large that amplifiers pertaining to the pulse transducer are unabledeliver sufficient energy, the oscillator stops, and the fieldcollapses. In this way “no object in the active zone of the sensor” or“the presence of an object in the active zone” can be detected in theform of oscillations with large amplitude or oscillations with smallamplitude, and corresponding pulse trains are delivered.

Thus, movement of a metal part, e.g. a tooth on a rotating gear wheel,can be detected as it moves through the active zone of the sensor. Sincethe detection is contactless, no mechanical wear occurs and the sensorcan be protected from dampness and dirt inside a casing. Switchingbetween high amplitude and low amplitude may be effected with highfrequency and detection is therefore accurate.

Other types of sensors can also be used in the conveyor in accordancewith the present invention, e.g. sensors in the form of capacitive pulsetransducers, as well as sensors comprising Hall elements, in order todetect rotation of the wheel or driving motor in question, and deliver acorresponding pulse train. The sensor may also be of the optical type,i.e., it may comprise a light source which emits a light ray towards areceiver, the light source and the receiver being arranged so that thelight ray is interrupted a predetermined number of times per revolutionof the wheel or driving motor in question, e.g. as a result of thepassage of teeth in a rotating gear wheel. A corresponding output pulsetrain is then obtained from the receiver. Other types of opticalsensors, emitting light and detecting reflected light from dark andlight bands, oriented perpendicular to the track of movement, e.g. on astrip along the track, can be used. The sensors may also be in the formof incremental transducers arranged to be stepped forward by the pulsesa predetermined number of steps per revolution of the wheel or drivingmotor in question. These transducers are often designed with inductiveor optical ensors.

In the embodiments described above, by way of example, the pulsetransducers are arranged in the drive motor or at gear wheels on theoutput shaft of the driving motor. The pulse transducers may also bearranged to detect rotation of the gear wheels over which the loadchains, 32 and 34, run, and rotation of the wheels supporting theconveyors, respectively, in the embodiments shown in FIGS. 2 and 3. Inprinciple the sensors can be arranged on any moving part in the motor.

Members are preferably provided to control the speed of travelingmovement of the conveyor and/or the speed of the carrier device. This ispossible since, because of the sensor, the location of the conveyor andthe carrier device, respectively, is known. The speed can thus graduallybe reduced so that “gentle” stop is achieved in exactly the desiredposition, preferably with the aid of so-called frequency operation. asdescribed above.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

What is claimed is:
 1. A conveyor system for use in baling paper pulp,comprising at least one conveyor including carrier means for carrying atleast one load, a frame for said carrier means, a track, wheel memberssupporting said conveyor for movement along said track from apredetermined reference position, a driving motor for moving saidconveyor along said track and sensor means for detecting a position ofsaid conveyor along said track with respect to said predeterminedreference position without direct contact therewith, said sensor meansdelivering a train of pulses corresponding to a predetermined distanceof movement of said conveyor along said track, whereby the position ofsaid conveyor along said track can be determined; wherein said sensormeans are positioned to detect the rotation of said wheel members alongsaid tracks or the rotation of said driving motor.
 2. The conveyorsystem of claim 1 wherein first sensor means comprise inductive pulsetransducers for detecting inductive changes and determining saidcorresponding train of pulses based thereon and said second sensor meanscomprises inductive pulse transducers for detecting inductive changesand determining said corresponding train of pulses based thereon.
 3. Theconveyor system of claim 1 including a plurality of detection pointsdisposed along said track for detection by said sensor means.
 4. Theconveyor system of claim 3 wherein said plurality of detection pointscomprise a plurality of openings evenly spaced along said track.
 5. Theconveyor system of claim 1 including speed control means for controllingthe speed of movement of said conveyor along said track based upon saidtrain of pulses determined by said sensor means.
 6. The conveyor systemof claim 1 wherein said carrier means comprises a chain conveyor.
 7. Theconveyor system of claim 1 wherein said driving motor comprises areversible driving motor, whereby the direction of movement of saidconveyor along said track can be reversed.
 8. A conveyor system for usein baling paper pulp, comprising at least one conveyor including carriermeans for carrying at least one load, a frame for said carrier means, atrack, wheel members supporting said frame for movement along said trackfrom a predetermined reference position, and sensor means for detectinga position of said conveyor along said track with respect to saidpredetermined reference position without direct contact therewith, saidsensor means delivering a train of pulses corresponding to apredetermined distance of movement of said conveyor along said track,whereby the position of said conveyor along said track can bedetermined; wherein said sensor means comprises inductive pulsetransducer means for detecting inductive changes and determining saidcorresponding train of pulses based thereon.
 9. A conveyor system foruse in baling paper pulp comprising at least one conveyor includingcarrier means for carrying at least one load, a frame for said carriermeans, said carrier means being movably supported on said frame formovement from a predetermined reference position, a plurality of motordriven gear wheels for movably supporting said carrier means withrespect to said frame and sensor means for detecting the position ofsaid carrier means with respect to said predetermined reference positionwithout direct contact therewith, said sensor means delivering a trainof pulses corresponding to a predetermined distance of movement of saidcarrier means with respect to said frame, whereby the position of saidcarrier means can be determined.
 10. The conveyor system of claim 1including a driving motor for driving said motor driven gear wheels, andwherein said sensor means are positioned to detect the rotation of saidmotor driven gear wheels or the rotation of said motor.
 11. The conveyorsystem of claim 9 including a plurality of detection points disposedalong said carrier means for detection by said sensor means.
 12. Theconveyor system of claim 11 wherein said plurality of detection pointscomprises a plurality of openings evenly spaced along said carriermeans.
 13. The conveyor system of claim 9 including speed control meansfor controlling the speed of movement of said carrier means along saidframe based upon said train of pulses determined by said sensor means.14. The conveyor system of claim 10 wherein said driving motor comprisesa reversible driving motor whereby the direction of movement of saidcarrier means with respect to said frame can be reversed.
 15. Theconveyor system of claim 9 including a plurality of end positionindicators for stopping movement of said carrier means along said frameat predetermined end positions.
 16. The conveyor system of claim 9wherein said sensor means comprise inductive pulse transducer means fordetecting inductive changes and determining said corresponding train ofpulses based thereon.
 17. A conveyor system for baling paper pulp,comprising at least one conveyor including a carrier device for carryingat least one load, a frame for said carrier device, said carrier devicebeing movably supported on said frame for movement from a firstpredetermined reference position, a track, wheel members supporting saidconveyor for movement along said track from a second predeterminedreference position, first sensor means for detecting a position of saidcarrier device along said frame with respect to said first predeterminedreference position without direct contact therewith, and second sensormeans for detecting a position of said conveyor along said track withrespect to said second predetermined reference position without directcontact therewith, said first sensor means delivering a train of pulses,each pulse corresponding to a certain distance of movement of saidcarrier device along said frame and said second sensor means deliveringa train of pulses, each pulse corresponding to a certain distance ofmovement of said conveyor along said track, whereby the position of saidcarrier device along said frame and the position of said conveyor alongsaid track can be determined.
 18. The conveyor system of claim 17including a plurality of motor driven gear wheels for movably supportingsaid carrier device with respect to said frame, a first driving motorfor driving said motor driven gear wheels, and a second driving motorfor moving said conveyor along said track, wherein said first sensormeans are positioned to detect the rotation of said motor driven gearwheels or the rotation of said first motor and said second sensor meansare positioned to detect the rotation of said wheel members along saidtrack or the rotation of said second driving motor.
 19. The conveyorsystem of claim 17 including a first plurality of detection pointsdisposed along said carrier device for detection by said first sensormeans and a second plurality of detection points disposed along saidtrack for detection by said second sensor means.
 20. The conveyor systemof claim 19 wherein said first plurality of detection points comprises aplurality of openings evenly spaced along said carrier device and saidsecond plurality of detection points comprises a plurality of openingsevenly spaced along said track.
 21. The conveyor system of claim 17including a first speed controller for controlling the speed of movementof said carrier device along said frame based upon said train of pulsesdetermined by said first sensor means and a second speed controller forcontrolling the speed of movement of said conveyor along said trackbased upon said train of pulses determined by said second sensor means.22. The conveyor system of claim 17 wherein said carrier devicecomprises a chain conveyor.
 23. The conveyor system of claim 18 whereinsaid first driving motor comprises a reversible driving motor, wherebythe direction of movement of said carrier device with respect to saidframe can be reversed, and said second driving motor comprises areversible driving motor, whereby the direction of movement of saidconveyor along said track can be reversed.